Deleterious Mutation Accumulation in Asexual Timema Stick Insects
Deleterious Mutation Accumulation in Asexual Timema Stick Insects
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DOI：
10.1093/molbev/msr237
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发表时间：
2012-01-01
影响因子：
10.7
通讯作者：
Crespi, Bernard J.
中科院分区：
文献类型：
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作者：
Henry, Lee;Schwander, Tanja;Crespi, Bernard J.
尽管相对于无性生殖而言，有性生殖的成本较高，但它仍然非常普遍，这表明它必须提供显着的优势。有性生殖和重组的一个假定的好处是，它们有助于清除轻度有害的突变，这些突变将在无性生殖谱系中积累，并导致它们的进化寿命较短。为了检验这一预测，我们估计的累积率编码（非同义）突变，这是预期有害的，在部分线粒体（COI）和两个核（肌动蛋白和HSP 70）基因在6个独立的无性系和相关的有性物种的Timema棒昆虫。我们在所有六个无性Timema和三个分析基因中的每一个中发现了编码突变积累增加的特征，与有性相比，无性者的编码突变积累率高出3.6至13.4倍。此外，由于无性系中的编码突变通常导致相关氨基酸位置处的相当大的疏水性变化，因此无性系中的编码突变可能与比有性系中更强烈的有害作用相关。我们的研究结果表明，有害的突变积累可以不同地影响有性和无性谱系，并支持有害的突变积累在限制所有女性谱系的长期持续性中起着重要作用的想法。
Sexual reproduction is extremely widespread in spite of its presumed costs relative to asexual reproduction, indicating that it must provide significant advantages. One postulated benefit of sex and recombination is that they facilitate the purging of mildly deleterious mutations, which would accumulate in asexual lineages and contribute to their short evolutionary life span. To test this prediction, we estimated the accumulation rate of coding (nonsynonymous) mutations, which are expected to be deleterious, in parts of one mitochondrial (COI) and two nuclear (Actin and Hsp70) genes in six independently derived asexual lineages and related sexual species of Timema stick insects. We found signatures of increased coding mutation accumulation in all six asexual Timema and for each of the three analyzed genes, with 3.6- to 13.4-fold higher rates in the asexuals as compared with the sexuals. In addition, because coding mutations in the asexuals often resulted in considerable hydrophobicity changes at the concerned amino acid positions, coding mutations in the asexuals are likely associated with more strongly deleterious effects than in the sexuals. Our results demonstrate that deleterious mutation accumulation can differentially affect sexual and asexual lineages and support the idea that deleterious mutation accumulation plays an important role in limiting the long-term persistence of all-female lineages.